Berlin 2005 – scientific programme

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CPP: Chemische Physik und Polymerphysik

CPP 17: Physics of polymers I

CPP 17.2: Talk

Tuesday, March 8, 2005, 10:00–10:15, TU C130

Stiffness variations across epoxy-interphases — •Martin Munz, Jaeun Chung, and Heinz Sturm — Bundesanstalt für Materialforschung und -Prüfung (BAM), Div. VI.2, Unter den Eichen 87, D-12205 Berlin

Interfacial effects in thermosetting systems are of particular interest, since significant diffusional effects can be induced during the crosslinking reaction. When starting from a two-component system consisting of an epoxy resin and an amine curing agent, stoichiometric imbalances can occur in the vicinity of the interface via the preferential ad- or absorption of one of the components. Via the crosslink reaction the chemical gradients are converted into spatial variations of the final network structure, thus resulting in gradients of local mechanical properties. In this study, scanning force microscopy (SFM) and depth-sensing micro-indentation were employed in order to map interphasial stiffness variations. Two different systems were employed, namely a copper/epoxy- and a polyvinylpyrrolidone(PVP)/epoxy-system. In the former case, SFM-based stiffness mapping revealed interphasial stiffness gradients extended over 3 microns. However, in the case of the thermoplastic/epoxy-system, much more extended interphases were found (210 microns). Using EDX, a zone of amine (diaminodiphenylsulfone, DDS) depletion was identified within the interphase and a non-zero amine-concentration was detected within PVP. The observation of local increase of epoxy modulus with a decrease of amine-epoxy concentration ratio is consistent with results from DMA. The observed increase of the room temperature modulus can be rationalised in terms of antiplasticisation of the beta transition.